A method of protecting surface mount capacitors from moisture and oxygen corrosion by applying a thermally curable pre-coat resin to a portion of the terminals of a capacitor and encapsulating the capacitor element(s) with a protective resin. The pre-coat resin is substantially rigid at ambient temperatures and flexible at elevated temperatures and is preferably a lactone-containing epoxy resin. The pre-coat resin may be applied to a solder coating-free portion of the terminals by brush or wiper prior to encapsulating the capacitor element(s) with the protective resin.
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9. A solid electrolytic capacitor comprising:
a solid electrolytic capacitor element connected to surface mount terminals;
a lactone resin applied to at least a portion of said terminals; and
a protective resin encapsulating said capacitor element and applied to a portion of said terminals over said lactone resin;
wherein said lactone resin is substantially rigid at ambient temperatures and flexible at elevated temperatures.
12. A method of manufacturing a solid electrolytic capacitor, said method comprising the steps of:
forming a solid electrolytic capacitor element;
applying a lactone resin to a portion of capacitor terminals;
connecting the capacitor terminals to the capacitor element; and
encapsulating the capacitor element and a portion of the capacitor terminals with a protective resin;
wherein said lactone resin is substantially rigid at ambient temperatures and flexible at elevated temperatures.
7. A method of protecting surface mount capacitors from moisture and oxygen corrosion, the capacitor having at least one capacitor element and terminals connected to the capacitor element, said method comprising the steps of:
applying a thermally curable lactone resin to a portion of the terminals of the capacitor; and
encapsulating the capacitor element with a protective resin;
wherein the lactone resin is substantially rigid at ambient temperatures and flexible at elevated temperatures.
1. A method of manufacturing a solid electrolytic capacitor, said method comprising the steps of:
forming a solid electrolytic capacitor element comprising an anode body;
applying a pre-coat resin to a portion of capacitor terminals;
connecting the capacitor terminals to the capacitor element; and
encapsulating the capacitor element and a portion of the capacitor terminals with a protective resin wherein said pre-coat resin covers said capacitor terminals where said protective resin encapsulates said anode body;
wherein said pre-coat resin is substantially rigid at ambient temperatures and flexible at temperatures above ambient temperatures.
2. A method of manufacturing a solid electrolytic capacitor according to
3. A method of manufacturing a solid electrolytic capacitor according to
4. A method of manufacturing a solid electrolytic capacitor according to
5. A method of manufacturing a solid electrolytic capacitor according to
6. A method of manufacturing a solid electrolytic capacitor according to
8. A method of protecting surface mount capacitors according to
10. A solid electrolytic capacitor according to
13. A method of manufacturing a solid electrolytic capacitor according to
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This application is a divisional application of U.S. patent application Ser. No. 10/365,209 filed Feb. 12, 2003 now U.S. Pat. No. 6,845,004.
This invention relates to protecting surface mount components from ambient environment, and more particularly to protecting resin-encapsulated capacitors from ambient moisture/oxygen.
With an ever increasing number of applications for electronics, surface mount technology has been used more frequently to construct electronic circuits. In surface mount technology, electronic components typically take the form of chip components having terminals for attachment by soldering to electronic boards. The terminals of the chip components require good solderability while also having heat resistance to withstand high temperatures during soldering and/or operation of the components.
Surface mount capacitors are generally protected from destructive effects of moisture and oxygen found in ambient environment by employing a seal formed by adhesion of a molding resin to a portion of a lead frame for the capacitor. As examples of conventional surface mount capacitors,
U.S. Pat. No. 6,229,687 (the '687 patent) proposes a method of preventing environment moisture and oxygen from accessing the capacitor element underneath the encapsulated resin. The '687 patent describes a solid electrolytic capacitor having an element that is prepared by forming an oxide layer, a conductive high polymer layer, and a conductor layer in succession on a valve metal. Lead frames of a selected metal are electrically connected to the valve metal and conductor layer, and a protective resin encapsulates the capacitor element and part of the lead frames. The surface of the lead frames contacting the protective resin has a roughened copper layer, and the protective resin has a thermal expansion coefficient that is close to the thermal expansion coefficient of the metal of the lead frames. The copper layer requires additional process steps and associated costs for forming the copper layer and sand blasting the layer for correct roughness.
A need exists for a method of preventing environment moisture and oxygen from accessing interior elements of surface mount components having resin encapsulation. More particularly, a need exists for a method of protecting resin-encapsulated capacitors from moisture and oxygen degradation of capacitor elements underneath the resin encapsulation that is relatively simple and inexpensive.
An object of this invention is to provide a method of protecting resin-encapsulated capacitors from moisture and oxygen degradation of capacitor elements encompassed by the resin encapsulation.
A more particular object of this invention is to provide a method of protecting resin-encapsulated capacitors from moisture and oxygen degradation of capacitor elements that is relatively simple and inexpensive to implement.
Another object of this invention to provide a method of preventing environment moisture and oxygen from accessing interior elements of surface mount components having resin encapsulation during mounting and operation of the components
Another object of this invention is to provide a resin-encapsulated solid electrolytic capacitor having a pre-coat resin applied to a portion of the terminals of the capacitor prior to resin encapsulation that prevents ambient moisture and oxygen from degrading the capacitor elements.
Another object of the invention is to provide a method of manufacturing a resin-encapsulated solid electrolytic capacitor having a pre-coat resin applied to a portion of the terminals of the capacitor prior to resin encapsulation that prevents ambient moisture and oxygen from degrading the capacitor elements.
These and other objects of the invention are accomplished by providing a method of protecting resin-encapsulated capacitors from moisture and oxygen degradation of capacitor elements encompassed by the resin encapsulation. The method includes applying a thermally curable pre-coat resin to a portion of the capacitor terminals and subsequently encapsulating the capacitor element with a protective resin. The pre-coat resin has the characteristics of being substantially rigid at ambient temperatures and flexible at elevated temperatures so that separation of the encapsulating resin from the terminals is prevented. The pre-coat resin is preferably a thermally curable epoxy resin, and more preferably a thermally curable lactone-containing epoxy resin mixture. During manufacture of the capacitor, the pre-coat resin is applied to solder coating-free portions of the capacitor terminals by wiping, spraying, or brushing the pre-coat resin onto the terminal portions.
Additionally, these and other objects of the invention are accomplished by providing a solid electrolytic capacitor having a solid electrolytic capacitor element connected to surface mount terminals, a pre-coat resin applied to a portion of the terminals, and a protective resin encapsulating the capacitor element and applied to a portion of the terminals over the pre-coat resin.
The present invention is a method of protecting resin-encapsulated capacitors from moisture and oxygen degradation of capacitor elements encompassed by the resin encapsulation. The capacitor element is connected to terminals for surface mounting. The method includes applying a thermally curable pre-coat resin to a portion of the capacitor terminals and subsequently encapsulating the capacitor element with a protective resin. The method uses the pre-coat resin to prevent separation of the resin encapsulation from the terminals. Additionally, the pre-coat resin prevents moisture and oxygen found in the ambient environment from accessing the capacitor element underneath the resin encapsulation. The present invention is also a resin-encapsulated solid electrolytic capacitor having a pre-coat resin covering a portion of the capacitor terminals between the capacitor element and the protective resin.
The capacitor element is formed according to conventional methods. For example, a valve metal foil is anodized in an aqueous electrolytic solution wherein the electrolytic solution is subjected to an anodizing voltage. The anodized foil is then cut into coupons of appropriate size, and then the coupons are welded to process bars. The edges of the coupons are preferably anodized in an electrolytic solution to coat the cut edges with anodic oxide. Alternatively, the metal foil is punched to form a comb-shaped electrode having projections, or coupons, and then anodized in the electrolytic solution. The coupons are then coated with a conductive polymer, such as by electrolytic polymerization, and preferably further coated with graphite and silver paint prior to assembly into finished capacitors. Each of the coupons is then cut to form a capacitor element. The capacitor element is attached to a lead frame, which subsequently forms the capacitor terminals, using conductive adhesive for cathode terminal attachment and/or laser welding or resistance welding for anode terminal attachment. The location of the lead frame with respect to the capacitor element depends on a desired anode or cathode attachment relative to the lead frame.
Although the invented capacitor is described with respect to a capacitor element based on a single valve metal coupon, the capacitor element may be also be formed with multiple coupons laminated together in accordance with conventional laminated capacitor techniques.
During manufacture of the invented capacitor, the pre-coat resin is applied to solder coating-free portions of the capacitor terminals by wiping, spraying, or brushing the pre-coat resin onto the terminal portions prior to encasing the capacitor element with the protective resin. The pre-coat resin has the characteristics of being substantially rigid at ambient temperatures and flexible at elevated temperatures so that separation of the encapsulating resin from the terminals is prevented. The pre-coat resin is preferably a thermally curable epoxy resin, and more preferably a thermally curable lactone-containing, such as butyrolactone, epoxy resin mixture.
This first embodiment is ideal for a preferred surface mount configuration of solid aluminum capacitors having conductive polymer cathodes. The configuration includes a stack of etched and anodized aluminum foil coupons partially coated with conductive polymer, graphite, and conductive paint layers and with the cathode coatings bonded together and attached to a lead frame with conductive adhesive to form a negative terminal. The uncoated ends of the etched and anodized coupons are welded to each other and to a portion of a lead frame to form a positive terminal after encapsulation and singulation of the device.
As best shown in
Those of ordinary skill in the art will be aware of other variations that are within the scope of the claimed invention, which is to be measured by the following claims.
Kinard, John Tony, Melody, Brian John, Wheeler, David Alexander, Stolarski, Chris, Chen, Qingping, Persico, Daniel F., Harrington, Albert Kennedy, Lessner, Phillip Michael, Pritchard, Kim
Patent | Priority | Assignee | Title |
10622160, | Mar 06 2017 | KYOCERA AVX Components Corporation | Solid electrolytic capacitor assembly |
11222755, | May 17 2019 | KYOCERA AVX Components Corporation | Delamination-resistant solid electrolytic capacitor |
11404220, | Sep 18 2019 | KYOCERA AVX Components Corporation | Solid electrolytic capacitor containing a barrier coating |
11915886, | Apr 25 2019 | KYOCERA AVX COMPONENTS BANGKOK LTD | Solid electrolytic capacitor |
9236192, | Aug 15 2013 | KYOCERA AVX Components Corporation | Moisture resistant solid electrolytic capacitor assembly |
Patent | Priority | Assignee | Title |
4594641, | May 03 1985 | Rogers Corporation | Decoupling capacitor and method of formation thereof |
5640746, | Aug 15 1995 | CTS Corporation | Method of hermetically encapsulating a crystal oscillator using a thermoplastic shell |
6229687, | May 27 1998 | MATSUSHITA ELECTRIC INDUSTRIAL CO , LTD | Solid electrolytic capacitor |
6235842, | Oct 08 1996 | Hitachi Chemical Company, Ltd. | Phase-separated carboxyl group-containing elastomer modified phoenoxy resin optionally with epoxy resin |
6236561, | Jun 18 1998 | MATSUSHITA ELECTRIC INDUSTRIAL CO , LTD | Chip type solid electrolytic capacitor and its manufacturing method |
6324051, | Oct 29 1999 | Matsushita Electric Industrial Co., Ltd. | Solid electrolytic capacitor |
6370016, | Aug 06 1997 | BC Components Holdings B.V. | Electrolytic capacitor cover method and materials for the manufacture thereof |
6686095, | Dec 28 1999 | Kabushiki Kaisha Toshiba | Gel electrolyte precursor and chemical battery |
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